Dept. of Psychology, Neuroscience, and Behaviour, McMaster University, and CIHR Training Program in Communication and Social Interaction in Healthy Aging

Christopher P. Taylor

Dept. of Psychology, Neuroscience, and Behaviour, McMaster University

Allison B. Sekuler

Dept of Psychology, Neuroscience, & Behaviour, McMaster University, and CIHR Training Program in Communication and Social Interaction in Healthy Aging, and CIHR Group in Sensory and Cognitive Aging, and Center for Vision Research, York University, Toronto

Patrick J. Bennett

Dept of Psychology, Neuroscience, & Behaviour, McMaster University, and CIHR Training Program in Communication and Social Interaction in Healthy Aging, and CIHR Group in Sensory and Cognitive Aging, and Center for Vision Research, York University, Toronto

Human visual function generally declines with age. Although some decline is caused by changes in the eye, changes in the brain also play a role (e.g., Bennett et al., 1999). Despite the importance of these age-related changes, fundamental questions about how neural changes affect processing in older brains remain unanswered. For example, although Leventhal et al. (2003) recently demonstrated decreased selectivity for visual stimuli orientation in V1 neurons in older macaques, researchers have never asked how aging affects orientation channels in older humans. Here, we used a notched-noise masking technique (Patterson, 1976) to address this question. A 2-IFC task (stimulus duration = 200ms; isi = 500ms) was used to measure detection thresholds for a horizontal Gabor target (sf=2.5 cpd) embedded in noise. The noise was broadband in terms of frequency and contained all orientations except for those within ± 0, 7.5, 15, 22.5, 30, 45, 60, 75, and 80 deg of horizontal. Detection thresholds decreased as notch width increased. Older observers (mean age = 69) yielded slightly higher thresholds at all noise-notch widths than did younger observers (mean age = 22). However, the shape of the masking functions did not differ across age groups, suggesting that the underlying orientation channels remain constant as a function of age. Currently, we are examining the effects of luminance on the tuning of orientation channels, and exploring whether tuning for other dimensions of visual patterns (e.g., spatial frequency) change as a function of age.